Phase II evaluation of vinblastine, methotrexate, and calcium leukovorin rescue in patients with refractory metastatic breast cancer.

Seventy-five evaluable patients with metastatic breast cancer refractory to frontline chemotherapy were treated with vinblastine 1.5 mg/m2 by continuous intravenous infusion for five days, intravenous infusion of methotrexate 200 mg/m2, and appropriate calcium leukovorin rescue. Thirty-eight patients were treated with vinblastine followed by methotrexate and calcium leukovorin, while 37 patients were treated with these same drugs in reverse sequence. In 17 patients (23%) an objective remission was achieved, while 39 remained stable for a period in excess of eight weeks. The median duration of remission was two months, and the median duration of survival was six months. The two regimens were well balanced for commonly used pretreatment prognostic factors. There was no difference in response rate and duration of response between the two treatment regimens. In patients with no prior exposure to methotrexate, the remission rate was 37% (11 of 30) compared with 13% (6 of 45). The treatment was well tolerated, and the dose-limiting toxicity was myelosuppression. This combination of drugs is effective in patients who have not been exposed to either drug, while it is only marginally effective in patients previously treated with methotrexate or vinblastine.